Correction instruments which apply a white correction fluid to a paper sheet have been used to cover up incorrectly written marks. Recently, correction instruments respectively using color correction fluids of different colors have been marketed and used for marking as well as for writing. Demand for such correction instruments has greatly increased with the expansion of the application field. A correction instrument in an early stage of development was a simple bottle-type desktop correction instrument having a bottle containing a correction fluid therein, and a stick incorporated into the cap and provided at its free end with a brush. Such a simple bottle-type desktop correction instrument has been replaced with a squeeze correction instrument having a flexible container containing a correction fluid, a head cap for closing the container, and an application tip, capable of discharging the correction fluid through the application tip when the container is squeezed between fingertips, free from the possibility of spilling the correction fluid even if the container is laid sideways and capable of preventing the correction fluid from solidification even if the container is left uncapped. Recently various inventions and devices have been proposed to prevent the drying of the correction fluid on the application tip to avoid troublesome work for removing the solidified correction fluid from the inside of the cap and the application tip every time the squeeze correction instrument is used.
As shown in FIG. 6, a correction instrument according to a previously proposed device disclosed in JP-U No. 62-29103 has a barrel assembly E comprising a flexible barrel 1 having a fluid tank portion 111 and a reduced front portion 11 of a diameter smaller than that of the fluid tank portion 111, having an open front end, a correction fluid 3 contained in the barrel 1, a stirring member 4 contained in the barrel 1, a head member 2 having a coupling portion 22 fitted on the front portion 11 of the barrel 1, an application tip 66 serving as a front end portion of the head member 2 and as a component of a valve mechanism, a coil spring 8 resiliently biasing the application tip 66 forward and an annular member 10 having a spring bearing portion 10a. The annular member 10 is provided with a center hole 10c of a size allowing the application tip 66 to slide therein and allowing the correction fluid 3 to flow therethrough and a flange 10b held between the front end surface 1a of the front portion 11 of the barrel 1 and a shoulder 22c formed in the head member 2. A cap 5 is detachably put on a head portion 222 of the barrel assembly E.
With the expansion of the field of use of correction instruments as mentioned above, there have been proposed various correction instruments employing a ball capable of drawing lines of a fixed width and of writing letters as an application tip. One of those previously proposed correction instruments is disclosed in JP-U No. 5-80791.
As shown in FIGS. 7A and 7B, a barrel assembly E included in a correction instrument disclosed in JP-U No. 5-80791 is assembled by putting a correction fluid 3 and a stirring member 4 in a barrel 1 having a fluid tank portion 111, and a reduced front end portion 11 of a diameter smaller than that of the fluid tank portion 111, having an open front end, putting a ball 6 in a ball holding tube 7 having an inside diameter slightly greater than the diameter of the ball 6 and having a front end 7a bent inward by swaging to keep the ball 6 therein, fitting the ball holding tube 7 in a front bore 2d formed in a head member 2, inserting a pressing member 88 in the ball holding tube 7 so that its front end is in contact with the ball 6, fitting an annular member 10 having a spring receiving portion 1a in a bore formed in the head member 2, extending a coil spring 8 between the back end of the pressing member 88 and the spring receiving portion 10a of the annular member 10 to apply a pressure to the pressing member 88 so that the ball 6 projects partly from the front end of the ball holding tube 7, and fixedly mounting a coupling portion 22 of the head member 2 on the front end portion 11 of the barrel 1. A cap 5 is detachably put on a head portion 222 of the barrel assembly E.
When using the prior art correction instrument according to the device disclosed in JP-U No. 62-29103, the pressure applied by fingertips to the flexible barrel is adjusted so that a desired quantity of the correction fluid is discharged through the application tip. When putting the cap of the correction instrument disclosed in JP-U No. 7-24470 on the body portion of the barrel assembly, air contained in the cap is compressed, and the compressed air flows into the barrel to maintain the interior of the barrel at an elevated pressure. When the application tip is pressed against a paper sheet or the like, the correction fluid is discharged automatically. Such, in outline, is the course of development of the correction instrument. The prior art correction instruments, practically, have both advantages and disadvantages, and there is still room for improvement in their performance and function.
Although it is difficult to provide a correction instrument capable of exercising performance and function meeting all the requirements of the user, the present invention is intended to provide a correction pen having the shape of a writing instrument capable similarly to writing instruments, of being carried in a clothing pocket, and incorporating therein improvements in the airtightness and strength of the joint of a barrel and a head member, in performance to secure smoothness in discharging a fluid and correction work, and in function to enable a cap to be removed from the barrel quickly and easily.
The barrel and the head member are joined together in an airtight fashion because the correction fluid contains an organic solvent. Most conventional correction instruments employ a joint structure like that shown in FIG. 6 or in FIGS. 7A and 7B in which the flange lob of the annular member 10 is held between the front end surface 1a of the barrel and the shoulder 22c of the coupling portion of the head member or employ an elastic packing to seal the joint. In view of the strength of the joint of the barrel and the head member, it is usual to use a screw joint by joining together the threaded front end portion of the barrel and the threaded coupling portion of the head member. However, a sufficiently strong screw joint cannot be formed if the barrel is formed by blow molding and, when the strength of the screw joint is particularly important, an adhesive must be used in combination with the screw joint, which requires troublesome work. Furthermore, the round screw joint of the barrel and the head member imposes restrictions on design.
In a correction instrument employing a ball as an application medium, and a ball holder having, similarly to the tip of a ball-point pen, a ball seat in a ball housing bore, such as disclosed in JP-U No. 7-24470, a space around the ball is liable to be clogged with the fluid. If the correction instrument has a barrel which can be compressed to discharge the fluid forcibly to clean the tip, the correction instrument is able to be quickly restored to its normal condition. If the correction instrument is of a type which maintains the interior of the barrel at an elevated pressure to discharge the fluid automatically, it takes time to restore the clogged correction instrument to its normal condition, and hence special consideration is required to put the cap in an airtight condition on the head member of the barrel assembly. A front end portion of the ball holding tube has a small wall thickness, the feel of the contact with a paper sheet is deteriorated, and the correction fluid cannot be uniformly applied to marks to be erased if a ball of a small diameter is used to draw a narrow line by a correction instrument like the correction instrument proposed in JP-U No. 5-80791 shown in FIGS. 7A and 7B, in which the ball lies behind the front edge of the ball holding tube.
To prevent the correction fluid from drying on the tip, the grasping force of the cap put on the head portion of the barrel assembly is higher than that of the cap of an ordinary writing instrument, and hence considerable force must be applied to the cap when putting the cap on and removing the same from the head portion of the barrel assembly. Therefore, it often occurs that the cap is put incompletely on the head portion of the barrel assembly and that the cap cannot be pulled properly and requires an unpleasant operation to pry the cap off the head portion of the barrel assembly. The correction pen of the present invention is provided with a clip on its cap and is intended to be carried in a pocket of clothes and hence the cap must be further firmly put on the head portion.